The ability to manipulate gene expression would provide a means of producing new characteristics in transformed plants. There are many situations for which high or increased levels of gene expression may be required: for example the production of important proteins for agronomical or commercial purposes, or the regulation of endogenous gene expression by competing levels of anti-sense RNA. The enhancement of transcription from promoters would facilitate these possibilities. Promoters vary in their transcription initiation rate and/or efficiency. Besides the transcription levels from a promoter other factors such as regulated or enhanced transcription should be considered. It is therefore of interest to provide DNA constructs which provide flexibility in the levels of expression obtained and under the appropriate conditions in which they are required to be effective.